prom-client 13.0.0 on Node.js NPM

[13.0.0] - 2020-12-16

changed: The following functions are now async (return a promise):
registry.metrics()
registry.getMetricsAsJSON()
registry.getMetricsAsArray()
registry.getSingleMetricAsString()
If your metrics server has a line like res.send(register.metrics()), you
should change it to res.send(await register.metrics()).
Additionally, all metric types now accept an optional collect function,
which is called when the metric's value should be collected and within which
you should set the metric's value. You should provide a collect function for
point-in-time metrics (e.g. current memory usage, as opposed to HTTP request
durations that are continuously logged in a histogram).
changed: register.clusterMetrics() no longer accepts a callback; it only
returns a promise.
removed: v12.0.0 added the undocumented functions registry.registerCollector
and registry.collectors(). These have been removed. If you were using them,
you should instead provide a collect function as described above.

fix: provide nodejs_version_info metric value after calling registry.resetMetrics() (#238)
fix: provide process_max_fds metric value after calling registry.resetMetrics()
fix: provide process_start_time_seconds metric value after calling registry.resetMetrics()
chore: improve performance of registry.getMetricAsPrometheusString
chore: refactor metrics to reduce code duplication
chore: replace utils.getPropertiesFromObj with Object.values
chore: remove unused catch bindings
chore: upgrade Prettier to 2.x
fix: startTimer returns number in typescript instead of void
fix: incorrect typings of `registry.getSingleMetric' (#388)
chore: stop testing node v13 on CI

feat: exposed registry.registerCollector() and registry.collectors() methods in TypeScript declaration
Added: complete working example of a pushgateway push in example/pushgateway.js
feat: added support for adding labels to default metrics (#374)
Added CHANGELOG reminder